1. Field of the Invention
The present invention is directed to semiconductor devices, and more particularly to controlling the propagation of photons through semiconductor structures.
2. Description of the Related Art
Light offers many advantages when used as a medium for propagating information, the foremost of which are increased speed and bandwidth. In comparison with electrical signals, signals transmitted optically can be switched and modulated faster and can include an even greater number of separate channels multiplexed together. Accordingly, lightwave transmission along optical fibers is widespread in the telecommunications industry. In an exemplary fiber optic communication system, a continuous wave (CW) beam of light may be emitted from a laser diode and modulated using an electro-optical modulator that is driven by an electrical signal. This electrical signal may correspond to voice or data which is to be transmitted over a distance between, e.g., two components in a computer, two computers in a network, or two phones across the country or the world. The light travels in an optical fiber to a location where it is detected by an optical sensor, which outputs voltage that varies in accordance with the modulation of the optical beam. In this manner, information can be rapidly transported from one location to another. To increase data throughput numerous optical signals at different wavelengths can be multiplexed and transmitted together along a single optical path. This optical path can be switched selectively and varied to direct the optical signals to the appropriate destination.
In constructing optical systems, such as the one described above, a variety of functionalities are desirable. One useful element is a modulator for varying a specific property of light such as amplitude or phase. Another valuable component is a tunable filter for selectively isolating certain optical frequencies. Additional useful elements are couplers and switches for controllably transferring light from one path to another. What is needed are advantageous designs and techniques for modulating and filtering light as well as for coupling and switching optical signals from one path to another.